Controllable pitch propeller



July 11, 1950 G. w. HARDY CONTROLLABLE PITCH PROPELLER 6 Sheets-Sheet 1 Filed NOV. 19, 1945 ATTOIQIVELY July 11, 1950 G. w. HARDY 1 2,515,037

CONTROLLABLE PITCH PROPELLER Filed Nov. 19, 1945 6 Sheets-Sheet 2 K. i J

July 11, 1950 e. w. HARDY 2,515,037

CONTROLLABLE PITCH PROPELLER 6 Sheets-Sheet 4 Filed NOV. 19, 1945 INVENTOR. 60:00 14/ flmem July 11, 1950 G. w. HARDY 2,515,037

CONTROLLABLE PITCH PROPELLER Filed Nov. 19, 1945 6 Sheets-Sheet 5 i T .N m/M I o W W m A N E w w\\ 6 n mm n July 11, 1950 G. w. HARDY CONTROLLABLE PITCH PROPELLER 6 Sheets-Sheet 6 Filed Nov. 19, 1945 INVENTOR.

14/ f/MW 1 W A r-v-a RA/L/ Patented July 11, 1950 CONTROLLABLE PITCH PROPELLER Gordon W. Hardy, Euclid, Ohio, assignor to The Marquette Metal Products Company, Cleveland, Ohio, a corporation of Ohio Application November 19, 1945, Serial No. 629,539

2 Claims.

This invention relates to a controllable or variable pitch propeller mechanism and to a fluid operated control system therefor which may be manually or otherwise actuated for adjusting the pitch of the blade or blades while the craft served by the'propeller mechanism is in flight or motion.

The objects include provision of a new or improved mechanism and control of that character. The present application shows a controllable pitch propeller mechanism very much on the order of that shown and claimed in my U. S. Patent Serial No. 2,491,375 issued December 13, 1949; and a further object is to provide, in connection with a propeller mechanism of the type there shown, an improved arrangement for preventing accidental movement of the blade or blades out of adjusted position.

A specific object is to. provide an improved anti-creep valve mechanism for the purposes outlined in the next preceding object.

Another object is to provide, in a hydraulic controllable pitch propeller, means for preventing application of such fluid forces to the blade adjusting servomotor and other fluid actuated mechanisms as might damage the servomotor or such mechanisms.

A further object is to provide control valve mechanisms in a fluid actuated controllable pitch propeller, which valve mechanisms are not subject to improper operation due to centrifugal forces acting on the valve elements.

A further object is to provide various improvements in relation to a releasable pitch limit control mechanism by which the blade pitch adjustment is normally limited within a certain angular range and by which the range may be increased for special operations such as feathering and reverse.

A further object is to provide a hydraulically actuated variable pitch propeller mechanism having an improved means for adjustably limiting the kinetic forces applicable in effecting blade adjustment during flight.

A further specific object is to provide, in a hydraulic variable pitch propeller mechanism, an

improved means whereby the tendency of the blades to return toward low pitch position is obstructed by an adjustable automatically operating limiting means enabling return movement only after the forces causing such tendency reach a predetermined set value.

A further object is to provide an improved fluid pumping and valving system for a hydraulically actuated variable pitch propeller mechanism.

Another object is to provide an improved cam 2 follower arrangement in an adjustable pitch propeller having a cam operated pumping and/or valving system for hydraulic pitch adjusting operation of the blades.

A further object is to provide an improved and simplified selectively and manually operable hydraulic actuating and controlling system for causing operation of blade pitch adjusting means to take place by power applied to the propeller to turn it.

Other objects and features of the invention will become apparent from the following description of the preferred form shown in the drawings, wherein:

Fig. 1 is a longitudinal assembly sectional view in a vertical plane centrally cutting the propeller mechanism and one blade mounting.

Fig. 2 is a transverse sectional view as indicated by the line 2-4 on Fig. 1, principally showing the blade pitch adjusting. servomotor arrangement.

Fig. 3 is a transverse sectional detail View taken along the line 33 on Fig. 1, showing the portion of a manually controlled pitch limit stop mechanism which is embodied in a master pitch adjusting and equalizing gear. 7

Fig. 4 is a transverse sectional assembly view taken as indicated by the line 44 on Fig. 1, showing the relative positions of the main pump and valve assembly units which either cause operation of the pitch adjustment of the blades in respective directions or release of a normal pitch limiting s op.

Fig. 5 is a detail plan view showing a fluid guide or ramp such as illustrated at the lower part of Fig. 4.

Fig. 6 is a subassembly sectional view taken at 66 on Fig. 4, showing a fluid pump and valve unit used to actuate the pitch limit stop mechanism.

Fig. 7 is a View similar to Fig. 6, showing one of two identical pump and valve units which actuate the pitch adjusting servomotor mechanism of Fig. 2 respectively in opposite directions.

Fig. 8 is a detail sectional assembly view taken as indicated by the line 8 on Fig. 2, showing the adjustable anti-creep valve mechanism.

Fig. 9 is a detail sectional assembly view taken along the line 9-9 on Fig. 2, showing the hydraulically actuated or servo portion of the pitch limiting stop mechanism. I I

Fig. 10 is a detail view of a labyrinth joint arrangement, being an enlargement of a portion of the mechanismshown at the lower right on Fig. 1 and taken on the same plane as Fig. 1

Fig, ll is a transverse sectional and elevational 3 view, the sectional part being as indicated by the line I l- -i l on Fig. 1, showing a preferred mounting arrangement for a set of concentric cams which actuate the movable elements of the pump and valve unit assemblies mentioned in connection with Figs. 6 and 7.

Fig. 12 is a partially schematic View showing parts of two cooperating hydraulic systems, one being rotatable with the propeller and the other being arranged for actuating the first system but not rotatable with the propeller and comprising a selective master control valve mechanism; for initiating operation of the different parts of the first system from a common point as on the-instrument panel of an aircraft. 7

Fig. 13 is a sectional view of the selective hydraulic actuator shown at the. right in Fig. ll and as indicated at l3i 3 thereon.

Fig. 14 is a partly sectional View of the actuator arrangement according to Fig. 1.3, the upper portion being out by the .plane indicated by line l t-e-llton Fig. 13-;

Referring further to Figs. l to the hub 2 is made as a high tensile steel shell (e. g. forged steel) having a generallyspherically formed hollow central portion 3; from which tubular integral arms or blade-supporting barrels ll extend radially, shown for example as three in number. The barrelsare spaced equally about the axis of rotation of the hub, which is to say the axis of an impeller shaft 5, Fig. 1, comprising; for example, part of the engine crankshaft. A forward portion of the engine crank shafthous-ing E is shown. The hub 2 is supported on the crank-shaft through the intermed-iary of a lightweight high tensile steel hub carrier 8 securely fastened to the hub and concentric therewith. v

A central tubular portion, of the carrier 6 is wedged onto and drivingly keyed as at r to a.

taperecl portion of the crankshaft. A tubular nut has its rearward end jammed against the hub carrier at 28'. The forwardly projecting tubular end of the nut 25 has a cross hole 2'! for a wrench bar.

The tubular central portion of the hub, carrier eatendsrearwardly asat 3. and forwardly as at 91 from a wall or web portion to, of the carrier, which latterportion is suitably shouldered as at I l for attachment to the hub. as by a series of screws. lt2' ('Fig'j l passing through the wallgor web Ill and into an inturned peripherally continuous rear flange it of the, hub machined to fit the shoulder surfaces H of, the carrier.

Surrounding and in spaced relation to the rearward tubular extension 8 of the carrier the wall" or web. it of the latter has an annular rearwardly projecting flange Mr of slightly less length than the tubular extension 8' and'concentric therewith, so that. the two portions 3 and I 4 and the supporting wall" or web Hr constitute a generally imperforate annular channel; The channel is bridged by a cover plate lli'and the annular space l8 so enclosed is hermetically sealedin part by the cover plate l5 through suitable; preferably soft metal, gaskets (not shown) squeezed; tightly between adjacent surfaces of the carrier portions 8 and M and inner and outer marginal surfaces of the plate l5 when the latter is attached to the carrier as-by appropriate screws. The screws l2; preferably have soft metal gaskets (or othersealing material, not shown) beneath their heads and forced against'the carrier wall or web ill: Further sealing for the space [6' is providedin connection with pump'and'valve units 2t, 2'! and 22 (see Figs. 1, 4, 6 and 7, later described) through 4 which the bodily rotated, pitch-adjusting hydraulic system. which is supplied with hydraulic fluid exclusively fromthe hermetically sealed an-' nular sump aifored by the space it, is caused to be operated in the desired manner as will be ex plained later.

A housing 30 for a blade adjusting servomotor generally indicated at 3! Figs. 1 and 2, is secured to' the forward face of the hub 2 centrally there of as by a series of screws 32 which pass through a circular flange 33 of said housing 3!! into threaded openings in a forwardly disposed inturned flange 34 of the hub. A split cotter pin 35,

I positioned as shown by Fig. l, engages circumman illustrated in Fig. 3.

ferentially spaced recesses in the servomotor block 38 and the forward end of the nut 25 holds the latter against, turning out of seated position on the crankshaft.

The blades 8!) of the propelle have their shank portions swivelled inside the barrels i concentric therewith and radiating from a point C, Fig. 1, about which the spherically formed portions of the hub are generated. Secured to the i-nner ends of the blade shanks by suitable means more-fully shown and described in my prior applicaticn; identified above, are identical blade adjusting bevel gear sectors fill in zero backlash mesh. with complementary teeth of a master blade pitch ad= justing and equalizing gear 4|, concentric with the crankshaft 5- and journalled on the hub carrier G1 Only one blade mounting is shown, the others beingthe-same.

Each blade adjusting gear sector 48 Fig. 1, has a supporting-hub 8 ijournalled at its inner end-ctr one of a set, of radial projections 82 of the hubcarrier 6' as described. in my'sai'd eopending application. The blade 9 in sector hub 81- is connected to a split blade-retaining sleeve assembly 83' (two half shells) embracing and complementary to the usual annularly ribbed shankof the blade 8d and held'fast on the blade as by a clamping collar 86. Surrounding and retaining the split sleeve 83 is an inner tubular bearingrace sleeve 85* connected-to the hub 81- of the gear sector 49' as by a key 86. The-bearing sleeve 35 is turnably supported by a set of radial anti-friction bearing rollers 8'7; and anend-thrust-receiv-ing anti friction ball'bearing assembly-88 The balls of the bearing 88' areisecured in the blade mountin barrel a ofthe' hub by-an adjustable race-- forming nut assembly 89, adjustablylocked in the barrel tbya-pbropriate means.

The teeth ofthe master bladeadjusting and equalizing; gear M maybe partlyomitted in three places around" the gear circumference to save Weightas suggested at the upper part in Fig; 1; but when the propeller is designed for reverse pitch and feathering a nearly complete setof teeth is usually provided. A complete set is par- The master gear 4-1 has its principalradial-support at isen-the for- Ward extremity of the tubular portion 9 of thehub carrier, additional radial support at 4 4 onthe servorn'otor-block 3 0 and axialthrust support, opposed-to the blade gearthrust reactions, byreason of. abuttingthe servomotorblock-as at-42' over a comparatively Wide face of the master gear: The-generally tubular: hub portionfi of the master gear 41; surrounds with slight clearance the forwardly extending tubular portion of the nut 25,, so that the gear 4| does not normally receiv bearing;supportfrom-th'e nut.

The:blade pitch-adjusting servomotor as shown by Figs. land 2 comprisesparallel cylinders 45 and 46' formed or' provided in theblock-or hous.

ing '30 and sealed at their opposite ends as by removable threaded plugs or caps 48. The cylin ders 45 (Fig. 2) are intercepted midway between their ends by an axial bore 49 through the block 30 around the hub 44 of the master or power gear 4|. The hub 44 has formed thereon diametrically opposed sets of pinion or gear teeth 50 which mesh respectively with rack teeth 5| of double ended pistons 53 and 54 in the cylinders. A seal assembly 3 6 is provided around the outer end of the hub 44 of the master gear 4| to retain a supply of lubricant'for the meshing rack and pinion teeth and associated moving parts.

The pressure chambers Pl, P2, P3 and P4 of the servomotor cylinders (of. Figs. 2 and 12) are cross connected in the manner schematically shown in Fig. 12 by suitable bores 59 and 60 preferably formed in the servomotor block 30 so that pressure fluid supplied and discharged interchangeably through conduits BI and 62 will move the two pistons 53 and 54 simultaneously but in opposite directions in driving the master or power gear through the rack and pinion tooth connections. The manner of forming the necessary passages in the servomotor block is more clearly described in my U. S. Patent Serial No. 2,433,990 issued January 6, 1948.

The portions of the releasable pitch limiting stop mechanism which are carried by the forward portion of the hub are illustrated particularly by Figs. 3, 9 and 12, but in the latter view only schematically and in a different specific form for convenience only as will be described later. The stop mechanism normally prevents the blades from being shifted on their swivel mountings above and below maximum and minimum pitch angles appropriate for forward driving of the craft while, at the will of the operator, enabling pitch changing movement of the blades below minimum normal pitch for reverse as may be required for braking purposes and above or beyond maximum forward pitch for feathering of the propeller.

Referring to Fig. 3, the master gear 4| has on its rear side and indented forwardly therefrom three circumferentially extending contiguous flat surfaces 65, 66 and 61, the latter two of which are coplanar. The master gear, as turned by the pitch adjusting servomotor 3|, rotates clockwise to move the blades from low to high pitch and for feathering and counterclockwise to move the blades toward low pitch and controllably into reverse pitch position. The flat surface 65 is indented forwardly at radial abutment surfaces 65a and 651) with reference to the coplanar surfaces 66 and B1, and those surfaces in turn terminate circumferentially in opposite directions at steplike radially disposed abutment surfaces 66a and 61a.

In Fig. 9, an axially shiftable latch plunger 68 of a hydraulically releasable pitch limiting latch mechanism 69 has its rearward reduced cylindrical end portion 10 normally seated between the limiting shoulders 65a and 65b to limit rotation of the master blade adjusting gear for normal forward driving pitch adjustments. The position of the mechanism 60 with reference to the servomotor block is shown in Fig. 2. The latch plunger 68 moves parallel to the main rotational axis of the propeller. The reduced cylindrical end 10 of the latch plunger as shown in Fig. 9 has been moved out of the deeply recessed portion 65 ofthe gear so that the latch is in position to allow the gear to turn past its normal pitch changing positions, namely, within the limits of the abutments 65a and 652). Thus in that withdrawn position of the latch, the gear may be turned so that the reduced end 10 can traverse the surfaces 66 and 6'1 to their respective limits.

In the illustrated arrangement according to Fig. 9, the latch plunger 68 is withdrawn from its normal position between the abutments 65a. and 6512 by hydraulic action of fluid introduced as through a conduit 12 (see also Fig. 12) by a manually actuated power operated pump, and the latch is returned to initial position by a spring 13 axially opposing the hydraulic releasing operation. A guiding housing for the latch plunger is inset into the rear face of the servomotor block 30 and an axially forwardly extended stem portion 14 of the latch plunger has a fluid sealing piston head 15 operating in a cylindrical pressure chamber 16 aligned with the guidebore Tl for the plunger, but separated therefrom as by a wall 18 sealed against exit of fluid from the cylinder chamber 16 by a suitablesealing assembly 19. To operate the latch block 68 to master gear releasing position so that the gear can move to reverse and feathering positions, fluid is supplied from the sump |6 by the pump and valve unit 22 shown in Figs. 4 and 6. The pump and valve unit 22 is generally similar to the units 20 and 2| which supply and exhaust the cylinders of the servomotor 3|, and the characteristics common to the three units will be described only with reference to the unit 22.

The pump and valve unit 22, Fig. 6, comprises a main body 90 of generally cylindrical form with parallel flanges 9| and 92 and associated respective sealing rings 93 and 94. The seals of the flanges are forced respectively against the main wall members I0 and I5 which axially enclose the sump I6, Fig. 1, so that fluid cannot be released from the sump past the unit flanges 9| and 92 forwardly or rearwardly of the propeller. The sealing ring 93 seat against an annular stepped shoulder formed in the wall l0 and the sealing ring 94 is pressed firmly against the flange 92 when the plate I5 is secured in position on the hub carrier to close the sump space it.

Between the flanges 9| and 92 the side walls of the body 90 are cut away on both sides as at 95, principally to allow free passage of fluid in the sump circumferentially thereof from one side of the unit 22 to the other. The pump mechanism 96 of the pump and valve unit 22 operates under operators control to pump fluid from the sump |6 into an axial discharge bore 91 in a forward central extension 98 which forms part of the conduit 1'2, Figs. 9 and 12, part of which assembly is so identified on Fig. 6. The piping leads through the servomotor block 30 for connection with the duct portion 12 shown on Fig. 9 forwardly of the block.

Referring further to Fig. 6,the pump 9|icomprises a peripherally sealed piston or plunger I00 slidably mounted in an eccentric but axial bore |0| of the body 90, having a lateral inlet port I02 and a discharge duct I03, part of which extends to the bore 91 past a spring closed check valve |04 shown closing the outer end of the duct I03. The piston I00 has an operating stem I04 projecting rearwardly from the body for actuating the piston during and consequent upon rotation of the propeller and operation of the controls as will be described later. A high rate spring I05 returns the piston to the position in which shown" after each forward pumping movement of the piston. The check valve I04 retains the fluid forced pastitinto the line 12.

The operating-stem 104 of the pump 100 is thrust forwardly consequent; upon propeller rotation whenever the intermediate one of three ring cams III), III and II2 is swung forwardly about its associated fixed hinge mounting pivot. All three pivots are designated H3 at the lower right in Fig. 1 and lower left in Fig. 11, the pivots being carried on a fixed adapter plate [I4 rearwardly from the main closure plate I5 ofthe sump chamber I6 and parallel therewith, being mounted on the engine housing. When the ring cams are selectively swung forwardly about their pivots H3, the pump or valve stems of the units 20, 2| and 22, corresponding in radial osition to the forward faces of respective ring cams, are thrust forwardly parallel to the axis of rotation of the propeller once for each turn of the propeller by operative engagement of the forwardly inclined cam surfaces with the pump plunger or valve stems. I'he hydraulic means for selectively controlling the positions of the ring cams will be described later in connection with Figs. 1, 11,

13 and 14.

Referring again toFig. 6, the forward hardened, smooth, wear resisting face iIIa of the ring cam II I, which is positioned to operatethe stop release pump plunger I66, slidably engages very hard or wear resisting planar surface of a cylindrical button or block; H6, which is part of one of a set of identical tappet assemblies Ill, one for each pump plunger or. valve to. be actuated in controlling the propeller mechanism. The tappets are mounted for easy sliding movement in guide sleeves II 8 in parallel forwardly counterbored holes through the slump closure plate I5 as shown best in Fig. 1. a flange I I9 shouldered into the counterbore of its associated hole in the plate I5 and the flange is held thereby in light contactwith the associated body (e. g. 90') of the. pump and valve unit served. The guide sleeves II 8 do not present any sealing problem with referenceto the sump I6, since their forward ends lie within the areas sealed from the sump I6 by the sealing rings 64, Fig. 6, which are forced tightly against the plate I5 all around the bodies (e. g. 96)

In order that the smooth faces of th 'tappet buttons H6 will always ride flat against the actuating faces of the ring cams N0, the buttons are rockingly mounted in spherical sockets I of tappet barrels I2! in the guide sleeves. ably the cam follower buttons IIB are of very hard metal such as Carba-lloy set into mounting pieces or shoes I22 of self lubricating character such as Oilite bronze which furnish the necessary friction reduction so that the mountings will 5 always move very freely in the spherical sockets I20, without having to provide more than a small area of contact at thebutton faces between the cam followers and the ring cams. The mountings are held in the sockets by appropriate means such as slightly inwardly spung flanges I24 around cylindrical outer end portions of the spherical sockets.

In addition to the pump plungerassemblyand check valves I04, the unit 22 (Fig. 6) has a restricted discharge aperture or bleeder provided at I26 between a plug I2! and the bore I28 of the body 96 which carries the plug. The rearward end of the plug I21 seals the bore I23 at I29 and fluid discharged through the bleeder aperture I26 from a duct I30, I3I communicating with the duct or pipe I2 supplied by the pump 96 is returned to the sump through across passage or port I32 in the body 90. The efiective size of the bleeder aperture I26 is predetermined with'ref- Each guide sleeve has Prefererence .to the capacity of the piston chamber 16 of the pitch limit latch plunger assembly, Fig. 9, and the strength of the spring 13, so that after the latch plunger 68 has been Withdrawn from normal pitch limiting position to allow the master blade pitch adjusting gear to turn beyond the normal forward driving limits in either direction, the plunger will automatically return quickly to said normal pitch-limiting position between the stops 65a and 652) as soon as the gear has been moved back to bring the gear face 65 into alignment with the latch plunger.

In order that operation of the pump 56 will not damage any part of the latch control mechanism in the event the cam ring III is held in pump plunger. actuating inclined position longer than it should'be inorder to accomplish withdrawal of the plunger portion fill from the normal pitch limiting area defined between flat surface 65, Fig. 3, the unit 22, Fig; 6, is provided with a relief valve mechanism I35 comprising as shown a tubular body I36 sealed at both ends in a bore I31 of the body 96 parallel to the bores IUI and I28. For sealing purposes, the bod I36 has land portions I68 and I39 provided with peripheral sealing rings I40 and MI respectively and, between the lands, the body I3 6 has a reduced diameter portion I42 providing a space communicating with a port I32 beyond the plug I21 through alateral port I44 and an annular channel I45 in said plug. 'Ihebody I3 6 has a valve seat I46 in a bore I41 of the body leading to the conduit 12 beyond the check valve. I64 as by a flared open forward end of the body I36 and communicating oblique passage I48 intercepting the bore I36. .Slidably fitting an enlarged bore I49 of the body I36 is a plunger type valve plug I56 normally closing against the seat I46 at a frusto-co-nical end portion of the plunger. The plunger is forced against the seat by an accurately calibrated spring I52 maintained in position in an axial rearcavi ty of the plug by an adjustable closure plug I53 adjus'tably occupying the somewhat enlarged threaded portion of the'bore I49 of the body I 36.

The valve plug I is forced out of contact with its seat I46 wheneverthere is an over supply of fluid delivered by the pump plunger I66, Fig. 6, to the piston chamber 76 of the latch mechanism shown on Fig. 9, and when the plug is thus uns eated theexcessfiuid is dumped into the sump I6, partly through cross passages I54 in the wall of the body I36. I

In order to prevent loss of fluid from t e sump pastthe threads of the plug I53' and the valve body I36, the rear end portion of the bore I3! for the valve body has a sealing ring I55 set into an annular recess, part of which is formed in the body 95 and part in the valve body I36. The ring is pressed -int o its seat so as to cut off all possibility of loss of fiuid past the threads when the rear end closure plate I5 is attached to the hub carrier 6 to close the sump -I 6.

The operation of the latch meohanisnnwhen the cam ring I I I- is swung forwardly, is fairly well illustrated in Fig; 12. Attention is called to the fact, that the indentations 651:, 66a: and 61a: as shown on Fig l2 and which correspond to the indentations 65 and 61, Fig. 3, are illustrated as though associated directly with one of the servo motor pistons of the pitch adjusting servomotor mechanism 3|. The cam v ring III is schematically shown in position to actuate the pump 96 and withdraw the latch plunger 68 from latching position. The. acting end of the plunger, for illustrationpurposes, extends to the left in Fig. 12

instead of to the right as in Fig. 9 and is shown riding the surfaces 81:: to allow an abnormal pitch adjusting movement of the servomotor as necessary for feathering. To release the latch, a single pumping impulse is usuall sufficient, whereupon the cam ring is returned to initial position as shown in Fig. 9. I A feature of the valve I35, Fig. 6, is that no amount of centrifugal force due to high speed of rotation on part of the propeller Referring now to Figs. 1, 4, '7, 11 and 12, the

hydraulic pitch adjusting mechanism which retates with the propeller at all times and forms, with the servomotor and sump, a hermetically sealed system, includes the two pump and valve mechanism units 28 and 2| which are identical in construction, see Fig. 7, but the pump and valve elements of which occupy relatively reversed positions as shown best in Figs. 4 and 12, so that each of the actuatingring cams H8 and H2, when swung forwardly, operates only a pump I8 I of one unit and a fluid exhaust valve I82 of the other unit.

The body I88 of each pump and valve unit 28 and 2I and the pumps and relief valves in the body I88 preferably are identical with the corresponding elements in the bod 80, Fig. 6, already described. The principal corresponding parts are numbered the same as in Fig. 6. The pump I6I of unit 28 supplies pressure fluid to the displacement chambers P2 and P3 of the servomotor as shown on Fig. 12, and, meanwhile, the exhaust valve I82 of the unit 2| exhausts fluid from the displacement chambers PI and P4. Note that the outer cam ring portions of which are indicated at I I2 in Fig. 12, are in active position relative to earn ring IIIJ causing reciprocation of the pump plunger of unit 20 and opening of the exhaust valve of unit 2I. As more fully explained in my Patent No. 2,491,375 issued December 13, 1949, the pumping and valving operations of units 28 and 2I are so timed that the valve I BZ of each unit is always open before the pumping by the cooperating unit starts and continues to remain open until the pumping (forward motion of pump plunger) ceases.

The construction of the two exhaust valves I 82, see Fig. 7, is very similar to that employed in the prior application just mentioned, there being a poppet type valve plug I18 in a sleeve III filling the inner or forward end of the bore I28 of the body I88. The sleeve has a seat I'I2 for the plug and cross passages I I3 leading to the sump l8 through the port I32 around a reduced portion "4 of the sleeve. The guide stem. I is sealed at I'I=B around thebore of thesleeve in which the stem slides and the rear end of. the sleeve I14 has a similar peripheral seal I 1 against the adjacent portion of the main body bore which receives the valve sleeve. The plug I10 has a return or closing spring I18. The tappet assemblies II8-I2I for both the pumps 'IBI and valves I82 are the same as the assembly illustrated atthe right in Fig. 6, wherefore there is no angularity between the forward cam faces and follower shoe elements.

Because the pump I6I of the unit 2I lies near the center of rotation ofthe propeller and centrifugal force tends to move the hydraulic fluid in the sump I8 outwardly, a curvedv sheet metal ramp or deflector I88, Figs. 4 and 15, is disposed across the sump and inclined in a direction with reference to propeller rotation such that, in event of depletion of the fluid supply or failure fully to charge the system, there will nevertheless be adequate fluid maintained adjacent the inlet port I82 of that pump. The other pump inlets are farther from the center and require no similar deflectors. The shape of the deflector I88,Fig.. 5, is such that it can be installed and held in position without fasteners. The portion of reduced width at the left provides a shoulder l8I for support by the rear flange of the hub carrier to which the closure plate I5 is attached. The end of the deflector adjacent the shoulder I8I is inserted beneath one of the screws I2 and held thereby in position. The opposite end of the deflector has a bent tongue I 82 which is forced against the adjacent flat side of the associated body I88 of unit 2i when shoulders I83 defining the tongue are sprung past the circular end portions of the body It!) as the deflector is moved into the installed position about the already inserted 0P? posite end of the deflector as a pivot. H

The hermetically sealed hydraulic system may be charged with hydraulic fluid in various ways, but in order to insure filling of substantially all the spaces of the system it is only necessary to provide a single scalable filler inlet assembly I88 in one of the peripheral walls of the sump I8, as shown in Fig. 4 and Fig. 4a, and temporarily to vent both sides of the servomotor and the by draulic pitch limiting latch systems as by removing plugs thereof shown in various places. The servomotor 3| may be vented, for example, by loosening the hollow plugs 281 of the anti-creep valve assemblies I81 and I98.

The filler plug assembly I84 as shown particularly by Fig. 4a, comprises a threaded sleeve I85 which is permanently magnetic for reasons explained below. The sleeve has a suitable head for engagement with a wrench and the threaded shank of the sleeve is undercut as at I85 to support a sealing ring I88. The sealing ring is forced into a complementary circular recess in the wall I4 of the hub carrier when the sleeve is screwed into place. For quickly filling the sump and all the fluid receiving spaces connected therewith under pressure, the sleeve I85 may be removed so as to provide a fairly large filler opening. In that case, the fluid is strained through a fine mesh screen extraneous to the propeller and not shown. For final filling of whatever small Space of the sump remains to be filled and for replen ishing any slight leakage which may later occur in the hydraulic system, the sleeve I85 is provided with a central through bore I81 which is threaded to receive a closure cap screw I88. A seal I88 is provided beneath the head of the closure screw I88, the seal beingmounted on anundercut portion of the screw. beneath the head and occupying av circulardepression in the outer face of the sleeve I 85. At the inner end of the bore I81 a cup strainer I89 is secured as by solder. Forreplenishing the system at any time, the propeller is turned so as to present the filler assembly upwardly, the screw plug I88 is removed and hydraulic fluid then introduced through the bore I 81 and screen E88 as by means of an oil can.

During rotation of the propeller, the hydraulic fluid in the sump is in constant motion circumferentially of the wall Id of the sump provided in part by the rearflange of the hub, carrier wall 18 and, as since all the fluid in the system eventually passes over the wall I4, any ferrous particles picked up by the fluid inpassing through "H. the hermetically sealed system will be attracted and retained by the magnetic sleeve I85.

.It will be readily understood from the inspec- .tion of Figs. 17 and 12, that the check valves we .prevent retrogressive movement of fluid forced by the pumps I6! into the delivery ducts 6i and 62 respectivelyleading to effectively opposite ends of the servomotor displacement chambers while, at thesame time, the delivery lines are open to communicate at all times through the ducts I39 with the chambers within the valve sleeves I'll which normally are blockedfrom communication with the sump by the exhaust valve plugs am. At the same time, the ducts Hill are open to respective relief valves 1.3.5 through the duct passages I48 so that if the pumping .of either unit Bil or 2! is continued afterthe'latchplunger .68 (Figs. 9 and 12) has made contact with any one of the abutments 65a, 65b, etc, such pumping cannot damage the servomotors or any of the parts connected with the various communicating fluid lines. Again the plungers 15B are not subject to inaccurate operation either for sealing or unsealing the ports I45 ,by centrifugal force acting on the sealing plungers, and the sealing elfect of the plungers is preset through the carefully calibrated springs I152 so that relief of pressure in the delivery lines cannot occur at .a less pressure value than necessary to eflTec-t blade pitch adjustment under the most adverse conditions that may be reasonably expected.

In case the propeller is arranged for both forward and reverse pitch control, then both the delivery lines El and 62 (Fig. 12) are provided each with an adjustable anti-creep valve mechanism, the respective mechanisms being indicated at I9! and 15.8. One anti-creep valve is shown in detail in Fig. 8 and one schematically in Fig. 12. Each mechanism I91 and 198 comprises a plunger slidably sealing, .atEfill, a bore 2m in the servomotor block between the opposite ends of the bore and maintained normally against the bottom of said bore (right, Fig. 8) by a calibrated spring 202. holding the plunger in such seated position with an initial. force, for example of 400 p, s. i. Each plunger has an axial bore 20% containing a spring-seated, nonreturn or check valve plunger 294 which. admits fluid from the feed line 6.! or 62 to the servomotor from the pump of the respective unit 20 or 21 comparatively freely but normally blocks return flow from the portion 6 la or 624; leading from the anti-creep valve to the servomotor. Return flow can only occur when the pressure tending to create such flow is inoreasedto a point somewhat greater than that nesisted by the spring 202 (i. e. greater than the assumed 409 p. s. i.). When that occurs, the plunger 20!! is forced forwardly of the propeller (left, Fig. 8) by such greater pressure, and an adjustable check valve release pin 205 forces the plug 204 of the check valve olf its seat to enable escape of fluid from the delivery line portion Bla or 620. to the forward end. of the bore 20!, hence to the portion of the said line GI or 62 leading back to the unit 2!! or 2i. The pin 205 is screw threaded for adjustment at 206 into a removable plug 201 which closes the forward end of the bore 26! in the servomotor block. Adjustment of the release pins 205 can be effected by removal of the spinner cap S, Fig. 1, whereupon access to the threaded portions of the release pins is enabled through hollow threaded portions of the plugs 201 by removal of closure screws 208 of respective units 191 and I98.

It will be seen that return flow from the servomotor displacement space PI, for example, see

Fig. 12, through the anti-creep valve mechathe plungerzflfl a sufficient distance to cause the plug 204 'to be unseate'd. Additionally, it is necessary that the exhaust valve IE-2 be open simultaneously. Normally, as heretofore stated, the'valve I62 would'be open only when the pump I61 of unit 20 is operating. Thus there is a double check against movement of the servo-- motor 'by "the blades out 'of adjusted position by air impact on the blades, first by the anti-creep valve mechanism and second by the normally closed valves Itl. of the respective units it and 2.1. l vhen the propeller is designed only'fo-r forward pitch and/or feathering, but not reverse, one of the anti-creepvalve mechanisms I 97 and H18 is omitted from the construction.

Referring again to the adapter I I4, Fig. 1, on which the cam rings I Ill to II 2 are mounted, "the adapter and the sump closure plate I5 carry respective parts of a labyrinth seal 2'! 0, shown best infFig. 10, and which as shown by Fig. 11 extends entirely around the circular surface be tween the adapter and end plate. The labyrinth seal comprises 'a pair of relatively thin annular rings 21 "I and 212 maintained 'in spaced relationship to each other by a spacer ring 2M all se cured to "the entire enveloped peripheral surface portion of the adapter plate H4 as by a series of screws, one of which is indicated at 213. The thus spaced apart forwardly extending marginal portions 2H" and 2I2' of the rings 2H and 212 slidably embrace between them a rearwardly ex" tending-annular "flange 2I5 of a, ring ZIG secured as by screws 2|! to the rear side of the sump closure plate l5. The working space of the ring cams and tappet buttons is thus closed by a sealing arrangement enabling free turning move ment of the propeller but which will contain a suitable lubricant such as sponge grease, the supply of which lasts indefinitely.

For operating the ring cams I I0, Ill and H2, respective s'lidable cam strips 1 H), II"! and I I2" are guidedfor vertical movement in suitable channels formed in the adapter I'M behind the ring came for engagement with complementary beveled rearwardly disposed surfaces of the ring cams. Lifting of the cam strips is "accomplished by individual servomotor units all of identical construction, one of which is as illustrated at 220 in Fig. 1, carriedon the adapter plate "4. Both the construction and operation of the servomotor units 220 are essentially the same as in my copending application 528,412. Each unit includes a vertically slidable piston plunger 22I bearing upwardly against the associated cam strip, a return spring 222 and an adjustable stop .223 positioned for engagement with the top of the associated cam strip.

For operating the cam actuating servomotor mechanisms 220, the fluid lines I I0", I I i" and H2" lead respectively to individually andselectively operable actuator pump units 236, 23l and 232, shown best on Figs. 13 and 14. The pump units 230 etc. are mounted for reciprocating movement in a common two part housing 234 positionable on the instrument board of the craft or in any other suitable location- The essential construction of each of the ump units is the same and one only, for example the unit .230 shown at the left in Fig. 14, will be described 13 in detail. Corresponding reference characters are applied to the other pumpunits.

The actuator arrangement for the pump units 230 and 232 is a rotary cam 235 acting selectively upon push rods 231 and 236 of the units 230 and 232 respectively and controllable as by suitable hand crank 24l rigidly coupled with the cam as by a shaft 242. Theactuator for the pump unit 23l which operates the pitch adjusting stop latch of Fig. 9 comprises a, slidable plunger 238 accessible from the same side of the housing 234 as the crank of the cam. Both the crank and the handle 238' of the plunger can beoperated simultaneously by one hand of the pilot or copilot. Turning of the crank 24! in a counterclockwise direction, Fig. 14, operates the push rod 231 for adjusting the propeller toward high pitch and feathering, and turning in a, clockwise direction operates the push rod 235 for adjusting the pro-- peller toward low pitch and reverse pitch,

Referring further to Fig. 14, both pump units 230 and 232 are shown as supplied with operating fluid from a common supply tank 245 formed in the top of the housing 234. The supply tank has a filler tube 246. Respective supply ducts for the pumps of units 230 and 232 are shown at 251 and 250, leading to normally open portions of the bores 252 in which the push rods 236 and 231 slide.

Referring to the left hand portion of Fig. 14, the push rod 231 has a short reduced diameter partly tubular stem 253 beyond a shoulder 254. The tubular part of the stem is axially open at its left end at 256 and has communicating cross passages 255. The short stem 253 extends part way through the central bore of a piston 251 slidably mounted within the axial bore 258 of a, connector fitting 259 threaded into the adjacent end of the body 234 as at 260, in alignment with the push rod 231. The bore 253 is larger than the guide bore of the push rod so as to provide an abutment shoulder at 262 for limiting the movement to the right on part of the piston 251. The piston has a sealing ring 261 in a suitable groove for sealing engagement with the bore 258. The bore 258 communicates always with the conduit H" and similar or operatively equivalent bores. of the other pump units similarly communicate always with their conduits Ill" and H2". Within the bore 258 is a return spring 253 for the piston 251 and the spring acts against one side of a flange 264 of a sleeve 265 open at both ends and provided with cross passages at each side of the flange. The tubular portions of the sleeve 265 are the same size as the stem 253 of the push rod 231 and one end of the sleeve is in axial abutment therewith as shown. Around the stem 253 and freely movable on it between the piston 251 and the shoulder 254 of the push rod is a sealing ring 266.

If the push rod 231 is moved to the left toward the piston 251 from the position in which shown the cross passages 255 and the annular passage between the stem 253 and the piston are both sealed from communication with the supply duct 25!. The shoulder 254 of the push rod 231 forces the sealing ring 256 axially and meanwhile radially against the stem 253 at the right of the cross passages 255 to effect both sealing operations. Thereupon, the chamber provided by the bore 258 is sealed off from the supply conduit 25! and. further movement of the push rod causes the piston to eject fluid from the bore 258 into the delivery line H0" leading to the associated ring cam actuating servomotor 220. When the push rod 231 is returned to its initial position, as by the return spring 253 acting to turn the cam clockwise (Fig. 14), said spring through the flanged sleeve 265 causes the piston to be returned to initial position. The push rod itself is moved to the right by abutment between the sleeve 265 and stem 253 of the push rod. The actuator fluid system is thus reopened for communication with thesupply tank.

When the cam 235 is turned in the counterclockwise direction described above and necessary to actuate the push rod 231, the push. rod 236 maintainsits initial position due to a concentric portion 235 of the cam. The cam has a similar concentric portion235 which rides idly against the push rod 231 when the cam is being turned clockwise to operate the push rod 236.

Referring further to the pump unit 231 of the pitch limit latch control, the feed line from the supply tank 245 may comprise a duct 21!), Fig. 11 only, the lower end of which enters a port 211 which is open to the space between the push rod 240 and the associated piston 251 of that pump unit. Actuation of the push rod 240 by withdrawal of the actuating plunger 238 to the right (Fig. 13) lifts the push rod 240 through the agency of the cam surface 239 of the push rod. At the lower terminus of the cam there is a flat shoulder 213 which in the fully withdrawn position of the plunger 238 rests upon a flat shoulder 214 of the control plunger 238 to cause the push rod 240 to remain in lifted ring-cam-actuating position. Thus the operator has only to pull out the hydraulic latch actuating control plunger 238 its full distance and leave it temporarily in that position while operating the crank 24! to cause adjustment of the propeller blades to the desired abnormal pitch, i. e. feathering or reverse. The return of the plunger 238 to initial position requires only enough manual movement to separate the flat surfaces 213 and 214 from mutual contact, whereupon the spring 263 acting through the inclined cam contact 239 returns the control plunger to neutral or inactive position.

I claim:

1. In a controllable pitch propeller. a hub, a blade mounted on the hub enabling blade pitch adjustment, a hydraulic servomotor connected to the blade to effect such adjustment, normal pitch limiting abutments connected with the servomotor and turned thereby when adjusting the blade, a hydraulically releasable latch adapted to be positioned between said abutments and to clear the same when released for enable pitch adjustment beyond a normal range, separate pumping systems rotatable with the propeller and connected respectively hydraulically with the pitch adjusting servomotor and releasable latch, controllable mechanism to actuate the pumps, and relief valves in both pumping systems to limit the amount of pressure which may be delivered to the servomotor and latch by the pumping systems.

2. In a variable pitch propeller, hydraulic mechanism rotatable with the propeller to adjust blade pitch in opposite directions during flight, separate pumping means rotatable with the propeller for actuating the hydraulic means in respective directions, hydraulically acting control means non-rotatable with the propeller for initiating operation of the pumping means, said control means comprising two control pumps and respective servomotors and means associated therewith enabling the servomotors individually to actuate the pumping means of the propeller, a cam for operating both control pumps, each of said control pumps having a return spring operaposition.

GORDON W. HARDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Seppeler Mar. 29, 1932 Hoover Dec. 10, 1935 Ruths et a1 Mar. 17, 1942 Blanchard et a1 1- Jan. 5, 1943 Rindfleisch et a1. May 25, 1943 Keller Mar. 7, 1944 Number Number Na e Date 'Marfiin e1; 21,1. 41-11., Jun .7, 1944 Hains 1. 1,." Sept. 5, 1944 Hoover -11 July 16, 1946 Haines Mar. 25, 1947 Hardy 7-"- Ja 1943 Hardy "1111",, Dec. 13, 1949 FOREIGN PATENTS Country Date Great Britain Feb. 25, 1938 Great Britain, Jan. 2, 1939 Great Britain Feb. 16, 1944 Germany Sept, 30, 1936 France Feb. 24, 193$ 

